Junior's deliverer! (5)
I believe the answer is:
stork
'junior's deliverer' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
This is all the clue.
Can you help me to learn more?
(Other definitions for stork that I've seen before include "Baby-carrying bird?" , "Bird that delivers babies?" , "Mythological baby-bringer" , "The baby bird, so to speak" , "Long-legged bird" .)